(i) INT 0 (Divide Error)-
This interrupt occurs whenever there is division error i.e. when the result of a
division is too large to be stored. This condition normally occurs when the
divisor is very small as compared to the dividend (or) the divisor is zero.
Its ISR address is stored at location: Type 0 x 4 = 00000H in the IVT.
(ii) INT 1 (Single Step)-
The µp executes this interrupt after every instruction if the TF =1
It puts µp in single stepping mode i.e. the microprocessor will get interrupted
after executing every instruction. This is very useful during debugging.
This ISR generally displays contents of all registers.
Its ISR address is stored at location: Type 1 x 4 = 00004H in the IVT.
(iii)
INT 2 (Non Maskable Interrupt)-
The microprocessor executes this ISR in response to an interrupt on the NMI
(Non mask-able Interrupt) line.
Its ISR address is stored at location: Type 2 x 4 = 00008H in the IVT.
(iv) INT 3 (Breakpoint Interrupt)-
This interrupt is used to cause breakpoints in the program.
It is useful in debugging large programs
This ISR generally displays contents of all registers
Its ISR address is stored at location: Type 3 x 4 = 0000CH in the IVT
(v)
INT 4 (Overflow Interrupt)
This interrupt occurs if the overflow flag is set
It is used to detect overflow error in signed arithmetic operations.
Its ISR address is stored at location: Type 4 x 4 = 00010H in the IVT
(B) Reserved interrupts (Type 5 to Type 31)
These levels are reserved by Intel to be used in higher processors like 80386, Pentium
etc. They are not available to the user
(C) Available interrupts (Type 32 to Type 225)
These are user defined, software interrupts.
ISRs for these interrupts are written by the users to service various user defined
conditions.
These interrupts are invoked by writing the instruction INT N.
Its ISR address is obtained by the microprocessor from location N x 4 in the IVT
Problem:
The contents of memory location 0000:008C are given below
0000:008C 12, 34, 56, 78, 90, 92
(a) What is the interrupt vector address for Type-23H interrupt?
(b) Find the address of ISR corresponding to INT 23H
(c) For which type of interrupt, the interrupt vector address is 0000:00C8H